Mineral water a not fattening

This is true, provided nothing is added to the mineral water. Mineral water from springs or manufactured from water, added salts and carbon dioxide, has no energy (kilojoules or kilocalories) and therefore, cannot contribute to body fatness

The sodium salts in mineral water add to total sodium intake. In some susceptible people this may increase blood pressure. Also, in some people, too much sodium may lead to the retention of fluid resulting in swelling for example, of the ankles. This can contribute to an increase in weight although it is not fat. It is advisable to choose low sodium mineral waters (less than 30 mill grams sodium per 100 ml or, as it is sometimes expressed, 300 ppm -parts per million). Even this is equivalent to having 115 milligram of sodium (or 5 mmole of sodium, see EXTRA SALT IS NEEDED DURING HOT WEATHER) in a 375 ml can. Drinking four cans would be like having 1 gram of sodium chloride or table salt.

Some mineral waters are now being flavoured are sweetened with sugar so that their energy value is the same as that of regular soft drinks. Unless sweetened with artificial sweeteners like aspartame, cyclamate, saccharin, plain mineral water is preferable.